US-led coalition against ISIL begins attack on Syria targets

The United States and its "partners" have launched bombing raids against Islamic State militants in Syria, where tens of thousands of people have fled to neighbouring Turkey as the jihadists advanced on a key border town.

US media reported five Arab states took part in the air raids as part of a new international coalition formed to attack the Islamic State group, which has seized swathes of territory in Syria and Iraq and committed atrocities including beheadings and crucifixions.

The US-led air assault in Syria marked a turning point in the war against the IS group, and came despite a threat by an IS-linked Algerian group to kill a French hostage if Paris failed to halt its aerial campaign against the IS in Iraq.

A Pentagon spokesman said the US military and unnamed "partner nation forces" have unleashed air strikes against the jihadists using fighters, bombers and Tomahawk missiles.

Earlier, Algerian group Jund al-Khilifa (Soldiers of the Caliphate) posted a video showing the white-haired and bespectacled French hostage, Herve Pierre Gourdel, squatting on the ground flanked by two hooded men clutching Kalashnikov assault rifles.

The footage was confirmed as authentic by the French government, and came after IS issued a statement urging Muslims to kill Westerners whose nations have joined a campaign to battle the jihadist group.

The United States has built a broad coalition of more than 50 nations to fight the IS jihadists, who have in recent days advanced towards a key border town in northern Syria, sending 130,000 terrified residents fleeing to Turkey.

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The strikes -- including Tomahawk missiles fired from naval warships at sea-- came less than two weeks after US President Barack Obama warned that he had approved an expansion of the campaign against the IS group to include action in Syria.

"I have made it clear that we will hunt down terrorists who threaten our country, wherever they are," Obama said on September 10 in a speech to the nation.

"This is a core principle of my presidency: if you threaten America, you will find no safe haven."

Australian fighter jets are expected to land in Dubai today to join the fight against ISIL. (9NEWS)

ABC News, citing a diplomatic source, named the partners in the Syria air raids as Bahrain, Jordan, Qatar, Saudi Arabia and the United Arab Emirates.

Washington began air strikes against IS targets in Iraq on August 8, with about 190 raids carried out against the extremists there.

Other Western powers have also vowed action against the jihadists, angered in particular by atrocities carried out by the militants, including brutal executions of British aid worker David Haines as well as US journalists James Foley and Steven Sotloff.

In a drive to enlist more partners to destroy the IS group, British Prime Minister David Cameron will hold face-to-face talks with Iran's President Hasan Rouhani -- the first such high-level meeting between the two countries since 1979.

In a statement posted online, IS spokesman Abu Mohamed al-Adnani said Muslims should seek out and kill Westerners whose countries have joined the coalition, in particular Americans and the French.

"If you can kill a disbelieving American or European... including the citizens of the countries that entered into a coalition against the Islamic State, then rely upon Allah, and kill him," he said.

France sought to reassure its citizens with Interior Minister Bernard Cazeneuve saying: "France is not afraid... France is prepared to respond to their threat."

Jund al-Khilifa, which has pledged allegiance to IS, raised the pressure on Paris with a threat to kill hostage Gourdel within a day.

The group said it had snatched the man in a mountainous region of eastern Algeria where Al-Qaeda is active and that it was responding to the IS call to target citizens of the coalition.

"The threats made by this group are extremely grave and demonstrate the extreme cruelty of (the IS group) and all those associated with it," French Foreign Minister Laurent Fabius said.

Foreign Minister Julie Bishop. (AAP)

On Monday, Australia said it was deploying warplanes to join the aerial campaign in northern Iraq.

The announcement comes after Australian police last week foiled an alleged plot by IS jihadists to conduct "demonstration killings" in the country, including randomly beheading members of the public.

Foreign Minister Julie Bishop said Canberra was treating the call as a genuine threat and stressed her country's committing to "containing and degrading and destroying" the jihadist group.

Canada, another member of the coalition, said it was looking to scale up its fight against terrorism.